There's fewer than 800 Mountain Gorillas left in the entire world, and their survival depends in part on people willing to pay money to go see them. But all this human interaction is bringing gorillas into contact with dangerous diseases.

Although humans are most closely related to chimpanzees, gorillas rank a very respectable second, sharing about 98% of their DNA with us. The current zoological consensus is that there are two distinct species of gorillas, western and eastern, and these are further divided into two subspecies each.

While all the gorilla species are to some degree threatened, the population levels vary wildly. There are at least 100,000 Western Lowland Gorillas in the wild, and 4,000 in zoos, while fellow western subspecies, the rarely seen Cross River Gorilla, is thought to have a remaining population of just 280. As for the eastern subspecies, the Eastern Lowland Gorilla has a relatively healthy population of about 4,000.

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And then there's the Mountain Gorilla. Estimates vary, but the consensus is that there's at most 800 left in the wild. Conservation efforts for this subspecies is especially difficult because their habitats are located in some of the region's most politically unstable areas, such as the Democratic Republic of the Congo, making the gorillas vulnerable to government corruption and even attacks from local militias, such as a 2007 incident in which Congolese guerrilla fighters in Virunga National Park killed and butchered a pair of adult gorillas.

Now, just to add to the intense difficulties of caring for the Mountain Gorillas, comes new evidence that the gorillas are susceptible to human diseases. Researchers at the Mountain Gorilla Veterinary Project have tracked a marked increase in respiratory illnesses in the gorillas over the past few years. These diseases can range from the gorilla equivalent of the common cold to full-on pneumonia, and these respiratory ailments are the second most common killer of the gorillas after traumatic injury.

Worse, tissue analysis has shown that two gorillas who died in recent disease outbreaks had the biochemical signature of an RNA virus known as human metapneumovirus, or HMPV - and with a name like that, you can probably guess which species they got it from. The disease may not have directly killed both of them, but it definitely weakened their immune system and left them significantly more vulnerable.

The problem is that human contact for these gorillas is pretty much unavoidable. Their small remaining natural environments happen to be located near some of Africa's most densely populated areas. And, in fact, human contact is arguably essential for their continued survival, as it's a vital source of funding for these parks - gorilla tourism brings in thousands of visitors each year from the local area and around the world to see the creatures up close.

For conservationists, it's a particularly brutal Catch-22, as one of the very things that allows these gorillas to enjoy even some small measure of protection from poachers and other forms of human encroachment - the national park system - is also bringing them into direct contact with deadly diseases. There's no clear answer here other than to remain vigilant in our role as stewards for this planet's endangered species...and I suppose hoping for the best can't hurt.